Medium Memory corruption exploit reference

CVE-2026-2240 — janet-lang janet compile.c janetc_pop_funcdef out-of-bounds

A vulnerability has been found in janet-lang janet up to 1.40.1. The impacted element is the function janetc_pop_funcdef of the file src/core/compile.c. Such manipulation leads to out-of-bounds read. The attack must be carried out locally. The exploit has been disclosed to the public and may be used. The name of the patch is 4dd08a4cdef5b1c42d9a2c19fc24412e97ef51d5. A patch should be applied to remediate this issue.

Published Feb 9, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: VulDB

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (medium)+3
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.18%

ahead of 7% of scored CVEs · Oct 14, 2026

Affects

Janet-lang

Janet

CVSS base

6.1

Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Janet-lang Janet).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Janet-lang	Janet	≤ 1.40.1	Vulnerable	NIST National Vulnerability Database
Janet-lang	Janet	version 1.40.0version 1.40.1	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
4.8	CVSS 4.0	Medium	—	—	VulDB via CVE Program (cve.org) e CISA ADP
1.9	CVSS 4.0	Low	—	—	cna@vuldb.com via NIST National Vulnerability Database
6.1	CVSS 3.1	Medium	1.8	4.2	nvd@nist.gov via NIST National Vulnerability Database
3.3	CVSS 3.1	Low	1.8	1.4	cna@vuldb.com via NIST National Vulnerability Database
3.3	CVSS 3.1	Low	—	—	VulDB via CVE Program (cve.org) e CISA ADP
3.3	CVSS 3.0	Low	—	—	VulDB via CVE Program (cve.org) e CISA ADP
1.7	CVSS 2.0	Low	3.1	2.9	cna@vuldb.com via NIST National Vulnerability Database
1.7	CVSS 2.0	Low	—	—	VulDB via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H (score shown at the top: nvd@nist.gov)

Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.1 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-125 · Out-of-bounds Read

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.18%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Affected products added · janet-lang/janet
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 6.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Feb 9, 2026 · VulDB

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

github.com/janet-lang/janet/commit/4dd08a4cdef5b1c42d9a2c19fc24412e97ef51d5
Patch, patch, NIST National Vulnerability Database
github.com/janet-lang/janet/issues/1702
Exploit, Issue Tracking, issue-tracking, NIST National Vulnerability Database
github.com/janet-lang/janet/
Product, product, NIST National Vulnerability Database
vuldb.com/
Permissions Required, VDB Entry, signature, permissions-required, NIST National Vulnerability Database
vuldb.com/
Third Party Advisory, VDB Entry, third-party-advisory, NIST National Vulnerability Database
github.com/oneafter/0123/blob/main/ja4/repro
Exploit, exploit, NIST National Vulnerability Database
github.com/janet-lang/janet/issues/1702
Exploit, Issue Tracking, issue-tracking, NIST National Vulnerability Database
vuldb.com/
Third Party Advisory, VDB Entry, vdb-entry, technical-description, NIST National Vulnerability Database

Elsewhere on this site

Janet-lang
every CVE for this vendor

Memory corruption
same class

CWE-125
other pages naming this weakness

Related CVEs (same products)

Low CVE-2026-10268 janet-lang janet marsh.c unmarshal_one_fiber integer overflow Jun 1, 2026
Low CVE-2026-10267 janet-lang janet debug.c doframe out-of-bounds Jun 1, 2026
Medium CVE-2026-2869 janet-lang janet handleattr specials.c janetc_varset out-of-bounds Feb 21, 2026
Medium CVE-2026-2241 janet-lang janet os.c os_strftime out-of-bounds Feb 9, 2026
Medium CVE-2026-2242 janet-lang janet specials.c janetc_if out-of-bounds Feb 9, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-2240 is "janet-lang janet compile.c janetc_pop_funcdef out-of-bounds", rated Medium. It affects Janet (Janet-lang); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.1 describes technical severity. EPSS 0.18% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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